Nursing Elites

1. Which of the following is NOT a recognized mode of natural selection?

• A. Directional selection (favoring one extreme trait value on a spectrum)
• B. Disruptive selection (favoring both extreme trait values on a spectrum)
• C. Stabilizing selection (favoring the average trait value on a spectrum)
• D. Sexual selection (selection based on mate choice that influences reproductive success)

Correct answer: D

Rationale: A) Directional selection is a recognized mode of natural selection where one extreme trait value on a spectrum is favored over others, leading to a shift in the average trait value over time. B) Disruptive selection is a recognized mode of natural selection where both extreme trait values on a spectrum are favored over the average trait value, potentially causing the population to split into distinct groups. C) Stabilizing selection is a recognized mode of natural selection favoring the average trait value on a spectrum over extreme values, resulting in reduced genetic diversity. D) Sexual selection differs from traditional natural selection modes as it involves mate choice and competition for mates, not direct selection pressure on traits affecting survival and reproduction in the environment. Sexual selection can drive the evolution of traits enhancing an individual's attractiveness for mating purposes.

2. Why are noble gas elements generally unreactive?

• A. They are too large and cannot form bonds easily.
• B. They lack valence electrons in their outermost shell.
• C. They have strong bonds within their own molecules.
• D. They have already achieved stable electron configurations.

Correct answer: D

Rationale: The correct answer is D. Noble gas elements are generally unreactive because they have already achieved stable electron configurations by having a full outer electron shell. This full shell makes them very stable and unlikely to gain, lose, or share electrons with other elements. Choices A, B, and C are incorrect because noble gases are not unreactive due to being too large to form bonds easily (A), lacking valence electrons in their outermost shell (B), or having strong bonds within their own molecules (C).

3. Which of the following best describes a chemical change?

• A. Melting ice to form water
• B. Dissolving sugar in water
• C. Burning wood to produce ash
• D. Crushing a can to reduce its size

Correct answer: C

Rationale: A chemical change involves a chemical reaction where new substances are formed. Burning wood to produce ash is an example of a chemical change because the wood undergoes a chemical reaction to form a new substance (ash). In this process, the chemical composition of wood changes to produce ash, which is a new substance. On the other hand, melting ice to form water, dissolving sugar in water, and crushing a can to reduce its size are examples of physical changes. In these instances, the substances may change their physical state or appearance but do not undergo a chemical reaction to form new substances. Therefore, choice C is the correct answer as it represents a chemical change, while choices A, B, and D represent physical changes.

4. Which property describes a substance's resistance to flow?

• A. Density
• B. Viscosity
• C. Conductivity
• D. Reactivity

Correct answer: B

Rationale: Viscosity is the property that describes a substance's resistance to flow. A substance with high viscosity flows slowly, while a substance with low viscosity flows quickly. Density (A) is the measure of mass per unit volume; conductivity (C) is the ability of a material to conduct electricity or heat, and reactivity (D) refers to how readily a substance undergoes chemical reactions. Therefore, the correct answer is B, viscosity, as it directly relates to a substance's resistance to flow.

5. Which of the following is a balanced chemical equation?

• A. H2 + O2 → H2O
• B. 2H2 + O2 → 2H2O
• C. 3H2O → 2H2 + O2
• D. H2O → H2 + O2

Correct answer: B

Rationale: A balanced chemical equation must have the same number of atoms of each element on both sides of the equation. In option B, 2H2 + O2 → 2H2O, the equation is balanced as there are 2 hydrogen atoms and 2 oxygen atoms on both the reactant and product sides after balancing, satisfying the law of conservation of mass. Option A is unbalanced as there are 2 oxygen atoms on the reactant side but only 1 oxygen atom on the product side. Option C is unbalanced with 3 hydrogen atoms on the reactant side and 2 hydrogen atoms on the product side. Option D is unbalanced with 1 oxygen atom on the reactant side and 2 oxygen atoms on the product side.

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